Humberside Police officers were initially suspicious about the the blaze at part of the Londesborough Hotel in the seaside town on Wednesday, October 17.A controlled demolition is having to be carried out.
But after a joint investigation with Humberside Fire and Rescue Service, the force has said the fire was "not suspicious".
A spokesperson said: "Initial indications were that the cause was a possible incident of arson.
"Due to the condition of the building a full investigation could not be carried out immediately because of difficulties in accessing the premises and concerns for safety.
"Sophisticated equipment has since been used which has found that the fire was not started deliberately.
"The building suffered significant structural damage. It has been made safe and a controlled demolition is now being carried out by its owners."